Simplify the following expression: $p = \dfrac{-9n}{9} - \dfrac{-6n}{9}$
Explanation: Since the expressions have the same denominator we simply combine the numerators: $p = \dfrac{-9n - (-6n)}{9}$ Combine like terms: $p = \dfrac{-3n}{9}$ Simplify by dividing numerator and denominator by 3: $p = \dfrac{-n}{3}$